The sunshine vitamin: Vitamin D

Written by Dr Arien van der Merwe MBChB FRSPH MISMA as an article excerpt from Health and Happiness, the newly revised and edited book written by Dr Arien, published by HSM Publishers, Jan 2013.

The body makes vitamin D when sunlight is absorbed by the skin. As long as people get enough exposure to the sun, it is not necessary to supplement with vitamin D. However, low vitamin D status is very common in the general population, with many research studies illustrating that few people fall within the optimal range for vitamin D. This is due to extremely low sun exposure, even in sunny countries. Globally, people are afraid of the sun and slather themselves with sunblock that further exacerbates the problem, blocking the skin from the sun’s beneficial rays. We need sun exposure for at least 30 minutes early morning and later afternoon, within an hour of sun rise and sun set.

Part of its role in the female reproductive system, is implicated in ovarian dysfunction (polycystic ovarian disease or PCOD) and its clinical manifestations may include obesity, increased insulin resistance with high insulin levels in the blood, low ovulation rates or lack of ovulation, with infertility. Studies regarding vitamin D status in patients with PCOD show that low vitamin D levels are linked with metabolic risk factors, e.g. insulin resistance, high BMI (body mass index) and WHR (waist-to-hip-ratio), triglycerides and high blood pressure – the classic symptoms of metabolic syndrome.

Populations especially at risk for low vitamin D status are infants, children, pregnant and postmenopausal women. Besides the classical diseases such as rickets, osteoporosis and osteomalacia, vitamin D deficiency in women might be associated with lower fertility and an increased risk for adverse pregnancy outcomes.

Vitamin D deficiency is often clinically unrecognised, however laboratory measurements are easy to perform, and treatment of vitamin D deficiency is inexpensive.

To summarise vitamin D’s functions in the body:

Cognitive protection – key to keeping mind sharp well into your golden years

Reduces the risk of breast cancer

Improves muscle strength

Supports immune system

Helpful in treating endometriosis

Prevents polycystic ovarian disease – PSOD

Important to prevent and treat insulin resistance, metabolic syndrome and the inevitable increase in weight, especially around the abdomen

Helpful in treating hypertension or high blood pressure during pregnancy (preeclampsia)

Plays an important role in fetal programming. Vitamin D induces more than 3 000 genes, many of which have a role in fetal development. Therefore, vitamin D may be particular relevant to the ‘developmental origins’ or ‘fetal programming hypothesis’ in which environmental factors such as vitamin D status in the mother, influence the genomic programming of fetal and neonatal developmental and subsequent disease risk in both childhood and adult life. In later life, children of mothers with low vitamin D serum levels during pregnancy, have a higher risk for developing certain chronic health challenges, such as asthma, schizophrenia, multiple sclerosis, type 1 diabetes mellitus and insulin resistance. This suggests intrauterine programming as possible mechanism. Epigenetic (above the gene, i.e. more important than the genetic expression itself, in the cell membrane or the environment of the cell), mechanisms that lead to persistent changes in structure and function in endocrine systems, are extensively being researched at present.

It is recommended to take vitamin D with calcium and magnesium for balance and the optimal absorption of all these important micronutrients. Vitamin D also improves the bioavailability of calcium. Take 300-600 IU of vitamin D with 600-900 mg calcium and 300-450 mg magnesium every evening.